Method for producing pulp fibres for saccharification, and aqueous solution of pulp fibres for saccharification

ABSTRACT

The purpose of the present disclosure is to provide a method for producing pulp fibres for saccharification from the pulp fibres of used sanitary items, said pulp fibres for saccharification having low lignin contents distributed within a narrow range, and enabling the production of pulp fibres for saccharification having superior saccharification properties. The production method according to the present disclosure is characterised by comprising the following: a step for supplying a mixed solution (51) containing pulp fibres and highly-absorbent polymers sourced from used sanitary items to a treatment tank (31) via a mixed-solution supply port (32); a step for supplying an ozone-containing gas (53) to a treatment solution (52) within the treatment tank (31) via an ozone-containing-gas supply port (43); a step for lifting the ozone-containing gas (53) whilst lowering the pulp fibres and highly-absorbent polymers within the treatment tank (31), thereby bringing the ozone-containing gas (53) into contact with the pulp fibres and highly-absorbent polymers, and forming pulp fibres for saccharification from the pulp fibres; and a step for discharging the treatment solution (52) via a treatment-solution discharge port (33). The method is further characterised in that the pulp fibres for saccharification have lignin contents of 0.1% or less.

FIELD

The present disclosure relates to a method of manufacturing pulp fibersfor saccharification from pulp fibers of used hygiene products, and toan aqueous solution of pulp fibers for saccharification which derivesfrom used hygiene products including pulp fibers and super absorbentpolymers.

BACKGROUND

Technologies for recycling hygiene products such as used disposablediapers, etc., have been studied.

For example, in Patent literature 1, a method of manufacturing recycledpulp which is reusable mainly as hygiene products is disclosed. Morespecifically, in Patent literature 1, a method of recovering pulp fibersfrom used hygiene products which include pulp fibers and super absorbentpolymers, and manufacturing recycled pulp which is reusable as hygieneproducts, the method comprising: a step of disassembling the usedhygiene products into pulp fibers and other materials, in an aqueoussolution which includes polyvalent metal ions or an acidic aqueoussolution with pH of 2.5 or lower, by applying physical force to the usedhygiene products, a step of separating the pulp fibers from a mixture ofthe pulp fibers which is generated in the disassembling step and theother materials, and a step of treating the separated pulp fibers in anozone containing aqueous solution with pH of 2.5 or lower, is described.

In Patent literature 1, the reason why the pulp fibers are treated withthe ozone containing aqueous solution is that a considerable amount ofthe super absorbent polymers remains in the separated pulp fibers, andthat the super absorbent polymers are oxidatively decomposed and aresolubilized, whereby being removed from the pulp fibers. In Patentliterature 1, as the method of treating the pulp fibers with the ozonecontaining aqueous solution, a method of putting the ozone containingaqueous solution in a treatment tank, and further putting the separatedpulp fibers in the ozone containing aqueous solution is disclosed. Insuch a method, at the time of treatment, a water stream is preferablycreated by moderately stirring the ozone containing aqueous solution, oran ozone gas may be blown into an aqueous solution put in the container,and a water stream may be generated in the ozone containing aqueoussolution by rising bubbles of ozone gas.

CITATION LIST Patent Literature

[PTL 1] Japanese Unexamined Patent Publication No. 2013-202021

SUMMARY Technical Problem

In Patent literature 1, a preferable manufacturing method of “recycledpulp fibers” which are reused as “pulp fibers for saccharification” isnot described.

In used hygiene products, in absorbent bodies, etc., which include pulpfibers and super absorbent polymers, (i) as the super absorbent polymersabsorb liquid, such as body fluid, etc., the super absorbent polymersenlarge and drag in the pulp fibers, and (ii) the enlarged superabsorbent polymers cause gel blocking, etc., while dragging in the pulpfibers, whereby there are many cases in which a plurality of superabsorbent polymers and a plurality of pulp fibers form a connectedstructure.

In such a case, it is discovered that although the method described inPatent literature 1 can disassemble the super absorbent polymers, etc.,which configure the connected structure into a state of being able to bedissolved, however, the method is not necessarily preferable for thepulp fibers which configure the connected structure to be reused as asaccharification solution.

Accordingly, the object of the present disclosure is to provide a methodof manufacturing pulp fibers for saccharification from pulp fibers inused hygiene products, which can manufacture pulp fibers forsaccharification that have low lignin content ratio and narrowdistribution thereof, and have excellent saccharification property.

Solution to Problem

The present inventors found out that a method of manufacturing pulpfibers for saccharification from pulp fibers of used hygiene products,comprising steps of: a preparation step of preparing a treatment tankwhich includes a liquid mixture supply port, and a treatment liquiddischarge port and an ozone containing gas supply port that are arrangedbelow the liquid mixture supply port, a liquid mixture supply step ofsupplying a liquid mixture which includes super absorbent polymers andthe pulp fibers that derive from the used hygiene products and water,from the liquid mixture supply port to the treatment tank, an ozonecontaining gas supply step of supplying ozone containing gas from theozone containing gas supply port to a treatment liquid in the treatmenttank, a pulp fibers for saccharification formation step of forming thepulp fibers for saccharification from the pulp fibers while dissolvingat least a portion of the super absorbent polymers in the treatmentliquid, by, in the treatment tank, raising the ozone containing gaswhile lowering the super absorbent polymers and the pulp fibers so as tomake the ozone containing gas come into contact with the super absorbentpolymers and the pulp fibers, and a treatment liquid discharge step ofdischarging the treatment liquid which includes the pulp fibers forsaccharification from the treatment liquid discharge port, wherein thepulp fibers for saccharification have a lignin content ratio of 0.1 mass% or less is the solution to the problem.

Advantageous Effects of Invention

The method of manufacturing pulp fibers for saccharification from pulpfibers in used hygiene products according to the present disclosure canmanufacture pulp fibers for saccharification that have low lignincontent ratio and narrow distribution thereof, and have excellentsaccharification property.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart which shows an embodiment of the method accordingto the present disclosure.

FIG. 2 is a schematic view which shows a configurational example of anapparatus of the ozone treatment process of FIG. 1.

FIG. 3 is a schematic view which shows another configurational exampleof an apparatus of the ozone treatment process of FIG. 1.

FIG. 4 is a schematic view which shows still another configurationalexample of an apparatus of the ozone treatment process of FIG. 1.

DESCRIPTION OF EMBODIMENTS

More specifically, the present disclosure relates to the followingaspects.

[Aspect 1]

A method of manufacturing pulp fibers for saccharification from pulpfibers of used hygiene products, comprising steps of:

a preparation step of preparing a treatment tank which includes a liquidmixture supply port, and a treatment liquid discharge port and an ozonecontaining gas supply port that are arranged below the liquid mixturesupply port,

a liquid mixture supply step of supplying a liquid mixture whichincludes super absorbent polymers and the pulp fibers that derive fromthe used hygiene products and water, from the liquid mixture supply portto the treatment tank,

an ozone containing gas supply step of supplying ozone containing gasfrom the ozone containing gas supply port to a treatment liquid in thetreatment tank,

a pulp fibers for saccharification formation step of forming the pulpfibers for saccharification from the pulp fibers while dissolving atleast a portion of the super absorbent polymers in the treatment liquid,by, in the treatment tank, raising the ozone containing gas whilelowering the super absorbent polymers and the pulp fibers so as to makethe ozone containing gas come into contact with the super absorbentpolymers and the pulp fibers, and

a treatment liquid discharge step of discharging the treatment liquidwhich includes the pulp fibers for saccharification from the treatmentliquid discharge port, wherein

the pulp fibers for saccharification have a lignin content ratio of 0.1mass % or less.

In used hygiene products, in absorbent bodies, etc., which include pulpfibers and super absorbent polymers, (i) as the super absorbent polymersabsorb liquid, such as body fluid, etc., the super absorbent polymersenlarge and drag in the pulp fibers, and (ii) the enlarged superabsorbent polymers cause gel blocking, etc., while dragging in the pulpfibers, whereby there are many cases in which a plurality of superabsorbent polymers and a plurality of pulp fibers form a connectedstructure.

In the method described in Patent Literature 1, although the ozonecontaining gas treats the free pulp fibers which do not form theconnected structure so as to decompose lignin which is included in thepulp fibers, since it is difficult for the ozone containing gas to comeinto contact with the pulp fibers which configure the connectedstructure, that is, the pulp fibers surrounded by the super absorbentpolymers, there may be cases in which the pulp fibers which configurethe connected structure cannot be sufficiently treated, that is, theremay be cases in which it is difficult for the lignin which is includedin the pulp fibers surrounded by the super absorbent polymers to bedecomposed. Accordingly, the recycled pulp fibers which are manufactureby the method described in Patent Literature 1 include those with broaddistribution of the lignin content ratio and high lignin content ratio.Further, in a case in which the used hygiene products that are to be theraw material include a plurality of types, for example, the same onetype of products (disposable diapers for adults) sold by differentcompanies, or different types of products (for example, disposablediapers for adults and disposable diapers for children) sold by the samecompany, the above-mentioned distribution of the lignin content ratiotends to be even broader. Incidentally, recycled pulp fibers with highlignin content ratio has a tendency that it is difficult for beingsaccharified.

The above-mentioned manufacturing method includes the predetermined pulpfibers for saccharification formation step, and in the pulp fibers forsaccharification formation step, while lowering the super absorbentpolymers and the pulp fibers, the ozone containing gas is raised, so asto make the super absorbent polymers and the pulp fibers come intocontact with the ozone containing gas. Among the free super absorbentpolymers, the free pulp fibers, and the connected structure, the freesuper absorbent polymers and the connected structure which haverelatively higher specific gravity tend to have higher sedimentationthan the free pulp fibers which have relatively lower specific gravity.On the other hand, since the ozone containing gas consumes ozone andrises while treating the super absorbent polymers and the pulp fibers,the ozone containing gas which is present in a lower position tends tohave higher ozone content ratio (that is, being fresher) than the ozonecontaining gas which is present in an upper position.

Incidentally, in the present description, the lowering speed relates tothe movement speed of the treatment liquid 52 in the treatment tank 31toward the lower portion, and generally is uniquely determined by afirst flow rate, a second flow rate, the size of the treatment tank,etc. On the other hand, in the present description, the sedimentationmeans the property of the pulp fibers, the super absorbent polymers andthe connected structure which are included in the treatment liquid 52 inthe treatment tank 31, expressing the ease of falling in the verticaldirection due to gravity, and in accordance with the specific gravity,etc., each of the pulp fibers, the super absorbent polymers, and theconnected structure has different sedimentations.

Accordingly, in the above-mentioned method, the free super absorbentpolymers and the super absorbent polymers in the connected structurewhich have relatively high sedimentation are oxidatively decomposed byfresher ozone containing gas so as to free the pulp fibers whichconfigure the connected structure, and further, the free pulp fiberswhich have relatively low sedimentation and taking relatively more timeto reach the treatment liquid discharge port can be treated with moretime by the ozone containing gas, so that the lignin included in thefree pulp fibers can be decomposed.

Further, generally, since the pulp fibers have a tendency that thehigher the lignin content ratio is, the higher the specific gravity is,in the above-mentioned method, the pulp fibers which have relativelyhigher lignin content ratio have relatively higher sedimentation thanthe pulp fibers which have relatively lower lignin content ratio, andthus fresher ozone containing gas comes into contact with the pulpfibers which have relatively higher lignin content ratio so as todecompose lignin included therein.

In the above-mentioned method, not only it is difficult for the pulpfibers for saccharification manufactured by the above-mentioned methodto broaden the distribution of the lignin content ratio, but also theabove-mentioned pulp fibers for saccharification includes the lignincontent ratio with a predetermined low concentration. Accordingly, inthe above-mentioned method, pulp fibers for saccharification that havelow lignin content ratio and narrow distribution thereof, and haveexcellent saccharification property can be manufactured.

[Aspect 2]

The method according to aspect 1, wherein the pulp fibers forsaccharification have a water contact angle of 20° or less.

When the hygiene products are recycled, it is easy for the oil contentof the hot melt adhesive agent included in the hygiene products to beabsorbed in the pulp fibers. Further, lignin included in the pulp fibershas a hydrophobic property.

In the method described in Patent literature 1, although the ozone inthe ozone containing gas can oxidatively decompose the hydrophobiccomponents such as the oil content of the pulp fibers which do notconfigure the connected structure, and lignin, etc., since it isdifficult for the ozone in the ozone containing gas to come into contactwith the pulp fibers which configure the connected structure, there mayhave been cases in which the hydrophobic components in the pulp fiberswere not sufficiently oxidatively decomposed.

Accordingly, when the recycled pulp fibers which are manufactured by themethod described in Patent literature 1 is used as the pulp fibers forsaccharification, especially when the recycled pulp fibers are dried, itmay be conceivable that it is difficult for the recycled pulp fibers tobe dispersed in an aqueous solution for saccharification, or it takestime to be dispersed.

According to the above-mentioned manufacturing method, since the pulpfibers for saccharification which are manufactured by theabove-mentioned manufacturing method have a predetermined water contactangle, the pulp fibers for saccharification which are manufactured bythe above-mentioned manufacturing method can be dried and stored, andthereafter, can be easily dispersed in a saccharification aqueoussolution. Accordingly, the above-mentioned manufacturing method canmanufacture pulp fibers for saccharification which are excellent insaccharification property.

[Aspect 3]

The method according to aspect 1 or 2, wherein the pulp fibers forsaccharification have a beating degree reduction speed of 300 mL/h ormore.

According to the above-mentioned manufacturing method, since the pulpfibers for saccharification have a predetermined beating degreereduction speed, in the subsequent saccharification step, it is easy forthe pulp fibers for saccharification to fluff when being applied withphysical force, that is, to be increased in the surface area, wherebycan be easily saccharified. Accordingly, the above-mentionedmanufacturing method can manufacture pulp fibers for saccharificationwhich are excellent in saccharification property.

[Aspect 4]

The method according to any one of aspects 1 to 3, wherein in the pulpfibers for saccharification formation step, the ozone containing gas issupplied from the ozone containing gas supply port as microbubbles ornanobubbles.

According to the above-mentioned manufacturing method, since ozonecontaining gas is supplied from the ozone containing gas supply port asmicrobubbles or nanobubbles, in the pulp fibers for saccharificationformation step, even in a case in which the super absorbent polymers andthe pulp fibers form a connected structure, the microbubbles ornanobubbles give buoyant force to the super absorbent polymers, theconnected structure and the pulp fibers, whereby the sedimentationsthereof decrease. Accordingly, it takes more time for the superabsorbent polymers, the connected structure and the pulp fibers to reachthe treatment liquid discharge port, so that ozone can decompose thefree super absorbent polymers and the super absorbent polymers whichconfigure the connected structure, and can sufficiently treat the freepulp fibers and the pulp fibers which configure the connected structure.Accordingly, the above-mentioned manufacturing method can manufacturepulp fibers for saccharification which are excellent in saccharificationproperty.

[Aspect 5]

The method according to any one of aspects 1 to 4, wherein the treatmentliquid is acidic.

According to the above-mentioned manufacturing method, the treatmentliquid is acidic (for example, having pH of 2.5 or lower). Accordingly,in a case in which the super absorbent polymers to be treated can beinactivated by an acid or the super absorbent polymers to be treated arealready inactivated, the super absorbent polymers can maintain the stateof being inactivated. Thus, even in a case in which the super absorbentpolymers and the pulp fibers form a connected structure, ozone in theozone containing gas can remove the super absorbent polymers whichconfigure the connected structure, and further, ozone in the ozonecontaining gas acts on the pulp fibers which configure the connectedstructure so as to reduce the lignin content ratio of the pulp fibers(form pulp fibers for saccharification which have low lignin contentratio).

Further, according to the above-mentioned manufacturing method, sincethe treatment liquid is acidic, it is easy for the treatment liquidwhich is to be discharged to be also acidic, whereby the dischargedtreatment liquid can be used in the saccharification step as it is, orafter slight adjustment. This is because, in a case in which thesaccharification step is performed, for example, under the presence of acellulase enzyme, it is preferable that the saccharification step isperformed not under an alkaline condition but under an acidic conditionso as not to inhibit the activity of the cellulase enzyme.

[Aspect 6]

The method according to any one of aspects 1 to 5, further comprising aninactivation step of inactivating the super absorbent polymers by anacid, before the liquid mixture supply step.

Since the above-mentioned manufacturing method further includes apredetermined inactivation step, even in a case in which the superabsorbent polymers and the pulp fibers form a connected structure, ozonein the ozone containing gas can remove the super absorbent polymerswhich configure the connected structure immediately after the liquidmixture which includes the super absorbent polymers that derive fromused hygiene products, the pulp fibers and water, is supplied to thetreatment tank, and further, ozone in the ozone containing gas acts onthe pulp fibers which configure the connected structure so as to reducethe lignin content ratio of the pulp fibers (form pulp fibers forsaccharification which have low lignin content ratio).

[Aspect 7]

The method according to aspect 6, wherein the acid is an acid which canform a complex with metal ions included in an excrement.

According to the above-mentioned manufacturing method, since the acid isan acid which can form a complex with metal ions included in anexcrement, it is difficult for the pulp fibers for saccharificationwhich are manufactured by the above-mentioned manufacturing method toinclude metal ions, whereby in a case in which the saccharification stepis performed, for example, under the presence of a cellulase enzyme, itis difficult for the activity of the cellulase enzyme to be inhibited bymetal ions.

[Aspect 8]

The method according to any one of aspects 1 to 7, wherein the pulpfibers for saccharification have an ash content ratio of 0.65 mass % orless.

According to the above-mentioned manufacturing method, since the pulpfibers for saccharification which are manufactured by theabove-mentioned manufacturing method have a predetermined ash contentratio, in a case in which the saccharification step is performed, forexample, under the presence of a cellulase enzyme, it is difficult forthe activity of the cellulase enzyme to be inhibited by metal ions.

[Aspect 9]

The method according to any one of aspects 1 to 8, wherein in the liquidmixture supply step, the liquid mixture is supplied continuously fromthe liquid mixture supply port to the treatment tank in a first flowrate, and in the treatment liquid discharge step, the treatment liquidis discharged continuously from the treatment liquid discharge port in asecond flow rate.

According to the above-mentioned manufacturing method, in the liquidmixture supply step, the liquid mixture is continuously supplied fromthe liquid mixture supply port to the treatment tank in the first flowrate, and in the treatment liquid discharge step, the treatment liquidis continuously discharged from the treatment liquid discharge port inthe second flow rate, whereby the treatment time of the super absorbentpolymers and the pulp fibers to be treated is equalized, thedistribution of the lignin content ratio in the pulp fibers forsaccharification is narrowed (with less variation), and as a result, inthe saccharification step, the pulp fibers for saccharification can beefficiently saccharified.

[Aspect 10]

The method according to any one of aspects 1 to 9, further comprising asaccharification step of saccharifying the pulp fibers forsaccharification, after the treatment liquid discharge step.

The above-mentioned manufacturing method can efficiently manufacture thesaccharification solution from the pulp fibers for saccharification.

[Aspect 11]

An aqueous solution of pulp fibers for saccharification which derivesfrom used hygiene products that include pulp fibers and super absorbentpolymers, wherein the pulp fibers for saccharification have a lignincontent ratio of 0.1 mass % or less.

According to the above-mentioned aqueous solution of pulp fibers forsaccharification, the pulp fibers for saccharification have apredetermined lignin content ratio, whereby are excellent insaccharification property.

[Aspect 12]

The aqueous solution of pulp fibers for saccharification according toaspect 11, wherein the pulp fibers for saccharification have a beatingdegree reduction speed of 300 mL/h or more.

According to the above-mentioned aqueous solution of pulp fibers forsaccharification, since the pulp fibers for saccharification have apredetermined beating degree reduction speed, in the subsequentsaccharification step, it is easy for the pulp fibers forsaccharification to fluff when being applied with physical force, thatis, to be increased in the surface area, whereby can be easilysaccharified.

[Aspect 13]

The aqueous solution of pulp fibers for saccharification according toaspect 11 or 12, wherein the aqueous solution of pulp fibers forsaccharification is acidic.

Since the above-mentioned aqueous solution of pulp fibers forsaccharification is acidic, in a case in which the saccharification stepis performed, for example, under the presence of a cellulase enzyme, itis difficult for the activity of the cellulase enzyme to be inhibited.

[Aspect 14]

The aqueous solution of pulp fibers for saccharification according toaspect 13, wherein the aqueous solution of pulp fibers forsaccharification includes an acid which can form a complex with metalions included in an excrement.

Since the above-mentioned aqueous solution of pulp fibers forsaccharification includes an acid which can form a complex with metalions included in an excrement, in a case in which the saccharificationstep is performed, for example, under the presence of a cellulaseenzyme, it is difficult for the activity of the cellulase enzyme to beinhibited by metal ions.

[Aspect 15]

The aqueous solution of pulp fibers for saccharification according toany one of aspects 11 to 14, wherein the pulp fibers forsaccharification have an ash content ratio of 0.65 mass % or less.

According to the above-mentioned aqueous solution of pulp fibers forsaccharification, since the pulp fibers for saccharification have apredetermined ash content ratio, in a case in which the saccharificationstep is performed, for example, under the presence of a cellulaseenzyme, it is difficult for the activity of the cellulase enzyme to beinhibited by metal ions.

Hereinbelow, the method of manufacturing a saccharification solutionfrom pulp fibers of used hygiene products (hereinbelow which may besimply referred to as “the manufacturing method of saccharificationsolution”) is explained.

Incidentally, the used hygiene products are hygiene products which areused by users, include hygiene products in a state of having absorbedliquid excrement of users, and further include those which have beenused but have not absorbed excrement, and those which have not yet beenused, etc.

First, a configurational example of hygiene products is explained. Ahygiene product includes a top sheet, a back sheet, and an absorbentbody which is arranged between the top sheet and the back sheet. As thehygiene products, for example, a disposable diaper, a urine pad, asanitary napkin, a bed sheet, a pet sheet, may be mentioned.

As the configurational material of the top sheet, for example, nonwovenfabric, or a film may be mentioned, and more specifically, liquidpermeable nonwoven fabric, a synthetic resin film which has liquidpermeation holes, and a composite sheet thereof, etc., may be mentioned.As the configurational material of the back sheet, for example, nonwovenfabric, or a film may be mentioned, and more specifically, liquidimpermeable nonwoven fabric, a liquid impermeable synthetic resin film,and a composite sheet of such nonwoven fabric and synthetic resin film,may be mentioned.

As the configurational materials of the absorbent body, an absorbentcore (for example, pulp fibers and super absorbent polymers), and a corewrap may be mentioned. As the pulp fibers, although not particularlylimited as long as they can be used in hygiene products, and forexample, cellulosic fibers may be mentioned. As the cellulosic fibers,for example, wood pulp, cross-linked pulp, non-wood pulp, regenerated,cellulose, semi-synthetic cellulose, etc., may be mentioned. As thesuper absorbent polymers (SAP), although not particularly limited aslong as they can be used in hygiene products, and for example, those ofpolyacrylate based, polysulfonate based, and anhydrous maleate based,may be mentioned.

One surface and the other surface of the absorbent body are respectivelyjoined to the top sheet and the back sheet through an adhesive agent. Ina plan view, the portion which extends to the outer side of theabsorbent body so as to surround the absorbent body (the peripheralportion) in the top sheet is joined to the portion which extends to theouter side of the absorbent body so as to surround the absorbent body(the peripheral portion) in the back sheet through an adhesive agent.Accordingly, the absorbent body is enclosed inside the joined body ofthe top sheet and the back sheet. As the adhesive agents, although notparticularly limited as long as they can be used in hygiene products andthe joining force thereof decreases due to softening with hot water, asdescribed later, and for example, a hot melt adhesive agent may bementioned. As the hot melt adhesive agent, for example, a pressuresensitive adhesive agent or heat sensitive adhesive agent made ofrubber-based materials such as styrene-ethylene-butadiene-styrene,styrene-butadiene-styrene, styrene-isoprene-styrene, etc., orolefin-based materials such as polyethylene, etc., may be mentioned.

FIG. 1 is a flowchart which shows the material separation method ofseparating the used hygiene products into configurational materials. Thematerial separation method is a method of separating the used hygieneproducts into films, nonwoven fabric, pulp fibers, and super absorbentpolymers. The material separation method includes the pretreatmentprocess S11, the disassembly process S12, and the separation processS13.

The pretreatment process S11 swells the used hygiene products withwater. The disassembly process S12 applies physical force to the swollenused hygiene products so as to disassemble the used hygiene productsinto films, nonwoven fabric, and core wraps, etc., and the absorbentcore (for example, the pulp fibers and the super absorbent polymers).The separation process S13 separates films, nonwoven fabric, the pulpfibers, and the super absorbent polymers from one another.

The manufacturing method of the saccharification solution according tothe present disclosure is included in the separation process S13 amongthe material separation method. Incidentally, in a case in which themixture of pulp fibers and super absorbent polymers is somehow obtainedin advance, process prior to the manufacturing method of thesaccharification solution in the pretreatment process S11, thedisassembly process S12, and the separation process S13, need not beperformed. Hereinbelow, each process is explained.

The pretreatment process S11 makes a plurality of used hygiene productsabsorb water so as to swell, in the same state as when recovered fromoutside, that is, in a state with no breaking or cutting, etc., and ifbeing in a rolled state or a folded state, remaining as they are, andfurther, without inactivating the super absorbent polymers of theabsorbent body. In the present embodiment, the used hygiene products aremade to absorb hot water so as to swell, or the used hygiene products ismade to absorb water so as to swell, and thereafter, the absorbed wateris heated so as to be hot water. The hot water is referred to as waterwith higher temperature than a normal temperature (20° C.±15° C. (5 to35° C.): JIS Z 8703).

Normally, the amount of liquid excrement which is actually absorbed inused hygiene products is extremely small compared to the maximumabsorption amount which the hygiene products can absorb (for example,approximately 10 to 20 mass % of the maximum absorption amount). In thepresent embodiment, in pretreatment process S11, by immersing the usedhygiene products in hot water, the used hygiene products are made toabsorb water up to an amount close to the maximum absorption amount ofthe used hygiene products (for example, 80 mass % or more of the maximumabsorption amount). Alternatively, the used hygiene products areimmersed in water with a normal temperature, are made to absorb water upto an amount close to the maximum absorption amount of the used hygieneproducts, and thereafter, the entire used hygiene products are heated toa temperature of hot water. Accordingly, the used hygiene products canbe brought to be in a state of being extremely swollen by hot water orwater with a normal temperature (hereinbelow, which may simply bereferred to as “hot water”). As a result, very high internal pressure isto be generated in the used hygiene products. Incidentally, the objectof making water the hot water is mainly for weakening the adhesive forceof the adhesive agent, as will be described later.

In a case in which the used hygiene products are initially in a state ofbeing rolled or folded so that the back sheet is placed on the outerside (with the top sheet being hidden on the inner side), by beingimmersed in hot water, the absorbent bodies of the used hygiene productsabsorb hot water in hot water and swell. As a result, the internalpressure of the used hygiene products increases, the force to opentoward the outer side is applied to the used hygiene products, wherebythe used hygiene products which are in the rolled state of the foldedstate open toward the outer side so as to be almost in a flat state.That is, the used hygiene products can be made into a flat expandedstate in the hot water. At this time, since the absorbent bodies haveabsorbed large amount of hot water and are extremely swollen, the usedhygiene products are in a state in which it is easy for the surfacethereof, that is, any of the portions of the top sheet and the backsheet which enclose the absorbent body to burst. That is, by thepretreatment process S11, the used hygiene products can be brought intoa state in which either of the surfaces is about to be torn and cut.Incidentally, in a case in which the used hygiene products are initiallyin a state of being flat and expanded, either one of the surfaces is toeasily burst as they are. Such a state cannot be brought in a case inwhich the used hygiene products have been broken, etc.

Further, by immersing the used hygiene products in hot water and/ormaking the used hygiene products absorb hot water, the adhesive agent(for example, a hot melt adhesive agent) used for joining each of theconfigurational materials can be softened by the heat of hot water,whereby the joining force of the adhesive agent can be decreased. Forexample, the adhesive agent which joins the peripheral portion of thetop sheet and the peripheral portion of the back sheet can be softenedby the heat of hot water, whereby the joining force of the adhesiveagent can be decreased. Further, the adhesive agent which joins the topsheet and the absorbent body, and the adhesive agent which joins theback sheet and the absorbent body can be softened by the heat of hotwater, whereby the joining force of the adhesive agents can bedecreased.

In this manner, in the pretreatment process S11, by the swell of theabsorbent bodies of the used hygiene products, the state in which anyportion of the surfaces of the used hygiene products is to burst, and astate in which the joining force of the adhesive agent is decreased, canbe brought. By the used hygiene products being brought into such astate, in the later-described disassembly process, the used hygieneproducts can be reliably disassembled.

The temperature of the hot water in the pretreatment process S11 is notparticularly limited as long as the adhesive agent of the used hygieneproducts can be softened, and for example, 60° C. or higher may bementioned, and preferably, the temperature is 70° C. or higher and 98°C. or lower. By setting the temperature of the hot water to 70° C. orhigher, the adhesive agent used for joining each of the configurationalmaterials can be softened by the heat of hot water, whereby the joiningforce of the adhesive agent can be decreased. By setting the temperatureof the hot water to 98° C. or lower, the hot water is reliably presentas liquid, whereby the used hygiene products can be reliably made toabsorb hot water. By the swell of the absorbent bodies and the heat ofhot water, the state of the surface of the used hygiene products beingabout to burst and the state in which the joining force of the adhesiveagent is decreased are more reliably brought. The measurement of thetemperature may be performed by measuring the temperature of hot waterin which the used hygiene products are immersed, or measuring theportion on an inner side by 5 mm from the surface of the used hygieneproducts which have absorbed water up to an amount close to the maximumabsorption amount (by inserting the tip of a temperature sensor).

Further, in reusing the used hygiene products, the sterilization of theconfigurational materials is very important. By setting the temperatureof hot water to 70° C. or higher, it is preferable since the effect ofsterilizing (disinfecting) the used hygiene products can be obtained.

The treatment time in the pretreatment process S11, that is, the timeduring which the used hygiene products are immersed in hot water, is notparticularly limited as long as the absorbent bodies of the used hygieneproducts can swell, and for example, is 2 to 60 minutes, and ispreferably 4 to 30 minutes. When the time is too short, the absorbentbodies cannot sufficiently swell, and when the time is too long, it willbe a waste of time and the treatment cost increases unnecessarily.

Further, the absorption amount of hot water by the absorbent bodies inthe pretreatment process S11 is not particularly limited as long as theabsorbent bodies can swell to such an extent that the used hygieneproducts can be disassembled in the later-described disassembly process,and for example, is 80 mass % or more of the maximum absorption amountof the used hygiene products, and preferably is 90 mass % or morethereof. Accordingly, the used hygiene products can be brought into astate of being swollen with being inflated with water. As a result, anextremely high internal pressure can be generated in the absorbentbodies of the used hygiene products.

Note that the maximum absorption amount is measured in the followingprocedures.

(1) Unused hygiene products are subjected to drying treatment in anatmosphere of 100° C. or higher, and the mass of the hygiene products ismeasured.

(2) In a case in which elastic materials which are capable of formingpockets so that it is difficult for water to reach the absorbent bodies(for example, elastic members surrounding the leg circumferences, thewaist circumferences, etc.) are arranged in the hygiene products, cutsare made in the elastic materials, whereby the hygiene products areflattened.

(3) The hygiene products are immersed in a water bath which is filledwith sufficient amount of tap water with the top sheet facing downward,and are left for 30 minutes.

(4) After being left, the hygiene products are placed on a net with topsheet facing downward, and after 20 minutes of draining, the mass of thehygiene products is measured.

Then, the mass difference before and after the hygiene products areimmersed in tap water is defined as the maximum absorption amount.

Subsequently, the disassembly process S12 gives physical impact on theplurality of used hygiene products which have been expanded and swollenby the pretreatment process S11, so as to disassemble the plurality ofused hygiene products into films (the back sheets), nonwoven fabric (thetop sheets), the core wraps, and further into the absorbent cores (forexample, the absorbent bodies and the super absorbent polymers).

The used hygiene products are brought by the pretreatment process S11 tobe expanded and flat, and portions of either of the surfaces are aboutto be torn by the swell, and in the present embodiment, especially bythe heat of hot water, the used hygiene products are brought to be in astate in which the joining force of the adhesive agent is decreased.Accordingly, in the disassembly process S12, the used hygiene productsin such a state are applied with physical impact, whereby among theportions of either of the surfaces, the joining portion of the top sheet(the nonwoven fabric) and the back sheet (the film) in which the joiningforce is especially decreased is torn off. Thus, the joining portion canbe torn (peeled) off. As the physical impact, although not particularlylimited, for example, a method of beating the used hygiene products on asurface which is made of a harder material than the used hygieneproducts, a method of, while sandwiching and letting the used hygieneproducts pass through a pair of rolls arranged so as to face each other,pressing the used hygiene products from both sides, etc., may bementioned.

In the present embodiment, the disassembly process S12 includes athrowing process of throwing the plurality of swollen used hygieneproducts in a bottom portion of a rotation drum with a horizontalrotation axis, and a beating process of rotating the rotation drumaround the rotation axis so as to repeat raising the plurality of usedhygiene products to the upper portion of the rotation drum and beatingthe used hygiene products on the bottom portion. Accordingly, physicalimpact can be added to the plurality of used hygiene products stably,continuously and easily. As the rotation drum, for example, a rotationdrum of a washing tub of a horizontal-type washing machine may bementioned, and accordingly, the disassembly process S12 can be performedby using an existing horizontal-type washing machine (for example,ECO-22B, manufactured by Inax Corporation). As the size of the rotationdrum, although not particularly limited as long as the above-mentionedimpact can be realized, the inner diameter and depth may for example be50 to 150 cm, and 30 to 120 cm, respectively. As the rotation speed ofthe rotation drum, although not particularly limited as long as theabove-mentioned impact can be realized, for example, 30 times/minute to100 times/minute, may be mentioned.

Further, although the temperature of the used hygiene products ismaintained relatively high by the hot water absorbed inside the usedhygiene products, from the viewpoint of suppressing the temperature dropof the adhesive agent, and maintaining the sterilization effect, thetemperature of the atmosphere inside the rotation drum is preferably 70°C. or higher, and is more preferably 75° C. or higher. The temperatureinside the rotation drum is, from the viewpoint of handling the usedhygiene products, preferably 98° C. or lower, and is more preferably 90°C. or lower. It is preferable that the amount of water inside therotation drum is as small as possible, and it is preferable that suchamount is small to an extent that the used hygiene products would not beunderneath the water surface at least in the bottom portion. When theused hygiene products are underneath the water surface, the impact onthe used hygiene products is absorbed by water, whereby it is difficultto give a desired impact on the used hygiene products. The time duringwhich the rotation drum is rotated is not particularly limited as longas the top sheets, the back sheets, and the core wraps, etc., and theabsorbent cores can be disassembled, and for example, 2 to 40 minutesmay be mentioned, and is preferably 4 to 20 minutes.

The joining portion of the top sheets (the nonwoven fabric) and the backsheets (the films) of the used hygiene products is busted and torn offby the physical impact. At the same time, through the gash, theabsorbent core (for example, the pulp fibers and the super absorbentpolymers) inside the used hygiene products erupts (pops out), by theinternal pressure of the absorbent bodies. Accordingly, the used hygieneproducts can be more reliably disassembled into the top sheets (thenonwoven fabric), the back sheet (the films), the core wraps, etc., andinto the absorbent cores (for example, the pulp fibers and the superabsorbent polymers).

Subsequently, the separation process S13 separates the plurality offilms (the back sheets), the plurality of pieces of nonwoven fabric (thetop sheets), the core wraps, etc., and the absorbent cores (for example,the pulp fibers and the super absorbent polymers), from one another.Note that the nonwoven fabric may be kept joined to the films. As theabove-mentioned separation method, although not particularly limited,for example, a method of using a sieve which does not let the topsheets, the back sheets, and the core wraps, etc., pass through and letsthe absorbent cores pass through, may be mentioned.

In the present embodiment, the separation process S13 may include,before separating the films, the nonwoven fabric, the core wraps, etc.,and the absorbent core, from one another, the inactivation process S31of inactivating the super absorbent polymers by an aqueous solutionincluding an inactivation agent, and the first separation process S32 ofseparating the films and the nonwoven fabric; and the mixture of thepulp fibers, the inactivated super absorbent polymers, and waste waterwhich is discharged from the super absorbent polymers by theinactivation; from one another.

In the inactivation process S31, before the first separation processS32, the top sheets (the nonwoven fabric), the back sheets (the films),and the absorbent bodies (the pulp fibers and the super absorbentpolymers) are immersed in an aqueous solution including an inactivationagent which is capable of inactivating the super absorbent polymers.Accordingly, the super absorbent polymers which have been attached tothe top sheets, the back sheets, and the pulp fibers can be inactivated.Thus, the super absorbent polymers in a state of high viscosity beforethe inactivation can be brought into super absorbent polymers in a stateof low viscosity, by dehydration caused by the inactivation.

As the inactivation agent, although not particularly limited, acid (forexample, an inorganic acid and an organic acid), lime, calcium chloride,magnesium sulfate, magnesium chloride, aluminum sulfate, aluminumchloride, etc., may be mentioned. The above-mentioned acid is preferablesince acid does not let ash be left in the pulp fibers. In a case inwhich acid is used as the inactivation agent, pH thereof is preferably2.5 or lower, and is more preferably 1.3 to 2.4. When the pH thereof istoo high, the absorption ability of the super absorbent polymers cannotbe sufficiently reduced. Further, there is also a possibility that thesterilization ability may be reduced. When the pH thereof is too low,there is a risk that the equipment may be corroded, and many alkalinechemicals are to be required for neutralization treatment during waterdischarged treatment.

As the above-mentioned inorganic acid, for example, sulfuric acid,hydrochloric acid, and nitric acid may be mentioned, although sulfuricacid is preferable from the viewpoint of not including chlorine and ofcost, etc. On the other hand, as the above-mentioned organic acid,citric acid, tartaric acid, glycolic acid, malic acid, succinic acid,acetic acid, ascorbic acid, etc., may be mentioned, although hydroxylcarbonate based organic acid such as citric acid, tartaric acid,gluconic acid, etc., which can form a complex with metal ions includedin an excrement is especially preferable. Incidentally, as the metalions included in an excrement, calcium ions may be mentioned. This isbecause, by the chelating effect of the acid which can form a complexwith metal ions included in an excrement, the metal ions in an excrementare trapped and can be removed. Further, citric acid has a cleaningeffect, whereby a high waste component removal effect can be expected.

Incidentally, since pH changes depending on water temperature, pH in thepresent disclosure is the one measured at the temperature of 20° C. ofan aqueous solution.

The treatment temperature of the inactivation process S31, that is, thetemperature of the aqueous solution including the inactivation agent, isnot particularly limited as long as the reaction of the inactivationproceeds. The treatment temperature may be room temperature, or may behigher than the room temperature, and for example, 15 to 30° C. may bementioned. Further, the treatment time of the inactivation process S31,that is, the time during which the top sheets, the back sheets and theabsorbent bodies are immersed in the aqueous solution including theinactivation agent, is not particularly limited as long as the superabsorbent polymers are inactivated and are dehydrated, and for example,2 to 60 minutes may be mentioned, and preferably is 5 to 30 minutes.Still further, the amount of the aqueous solution in the inactivationprocess S31, that is, the amount of the aqueous solution including theinactivation agent is not particularly limited as long as the reactionof the inactivation proceeds. The amount of the aqueous solution may be,for example, with respect to 100 parts by mass of the used hygieneproducts, preferably 300 to 3000 parts by mass, more preferably 500 to2500 parts by mass, and even more preferably 1000 to 2000 parts by mass.

In the first separation process S32, the top sheets (the nonwovenfabric), the back sheets (the films), the core wraps; and the mixture ofthe pulp fibers, the inactivated super absorbent polymers, and wastewater which is discharged from the super absorbent polymers by theinactivation; are separated from one another. Note that the waste wateris the moisture released from the super absorbent polymers by thedehydration of the aqueous solution including the inactivation agent inthe inactivation process S31, that is, the waste water including bodyfluid derived from an excrement and water derived from the hot water.

In the first separation process S32, the method of separating the topsheets, the back sheets, the pulp fibers, the super absorbent polymersand the waste water from one another is not particularly limited. Forexample, the products produced by the inactivation process (the topsheets, the back sheets, the pulp fibers, the super absorbent polymersand the waste water) may be discharged while being let to pass through ascreen with openings of 5 to 100 mm, and preferably of 10 to 60 mm.Accordingly, the pulp fibers, the super absorbent polymers and the wastewater are brought into the discharged water, while the top sheets andthe back sheets remain on the screen, whereby such products can beseparated. Incidentally, large shaped materials of other nonwovenfabric, films, etc. may remain on the screen. Especially, before theinactivation, since the super absorbent polymers are in a state withhigh viscosity, it cannot be said that it is easy to separate the superabsorbent polymers attached to the top sheets, the back sheets and thepulp fibers. However, after the inactivation, since the super absorbentpolymers are brought to a state with low viscosity by the dehydration,the super absorbent polymers attached to the top sheets, the back sheetsand the pulp fibers can be easily separated from the top sheets, theback sheets and the pulp fibers. Accordingly, the configurationalmaterials of the hygiene products can be efficiently separated andrecovered.

In the present embodiment, the separation process S13 may furtherinclude the second separation process S33 of, by a solvent whichdissolves the adhesive agent in the joining portions of films and othermaterials, removing the adhesive agent in the joining portions. In thepresent embodiment, by a solvent which dissolves the adhesive agent ineach of the joining portions of the films, the nonwoven fabric, and theabsorbent bodies, the adhesive agent in each of the joining portions isremoved.

In the second separation process S33, the adhesive agent in the joiningportions of the films (the back sheets) and other materials (thenonwoven fabric of the top sheets, the absorbent bodies remaining on thesurfaces of the top sheets and the back sheets, etc.) is removed by asolvent. Accordingly, the films and the other materials can be separatedfrom each other without breaking them and as they are. Thus, theconfigurational materials such as the films of the hygiene products canbe efficiently recovered. Further, since the films and the othermaterials can be separated from each other without remaining theadhesive agent on the films, the films can be brought to be reusable asresin with high purity. Accordingly, adverse effects caused by theadhesive can be suppressed when reusing the films. The same can be saidfor the nonwoven fabric.

As the solvent to be used in the second separation process S33, althoughnot particularly limited as long as it can dissolve the adhesive agent,for example, terpenes including at least one of terpene hydrocarbons,terpene aldehydes, and terpene ketones, may be mentioned. In thisprocess, an aqueous solution including terpene is used, and theconcentration of terpene in the aqueous solution is for example, 0.05mass % or higher and 2 mass % or lower. Preferably, the concentration is0.075 to 1 mass %. When the concentration of terpenes is too low, thereis a possibility that the adhesive agent in the joining portion may notbe dissolved. When the concentration of terpenes is too high, the costmay be too expensive. Further, not only does terpene dissolve anadhesive agent such as a hot melt adhesive agent, but also terpene hasoil stain cleaning effect. Accordingly, when printing is provided in theconfigurational materials of the hygiene products, such as the backsheets, etc., terpene can also decompose and remove the printing ink.

As the terpene hydrocarbons, for example, myrcene, limonene, pinene,camphor, sapinene, ferrandlene, paracymene, osymene, terpinene, karen,zingiberene, caryophyllene, bisabolene, cedrene, may be mentioned. Amongthese, limonene, pinene, terpinene, karen are preferable. Further, asthe terpene aldehydes, for example, citronellal, citral, cyclocitral,safranal, ferrandral, perilaldehyde, geranial, neral, may be mentioned.As the terpene ketones, for example, camphor, thujone, may be mentioned.Among the terpenes, the terpene hydrocarbons are preferable, andlimonene is especially preferable. There are three types of limonene:d-limonene, l-limonene, dipentene (dl-limonene), and all of these typescan be preferably used. The terpenes can be used singly of one type, orcan be used by combining two or more types thereof.

The treatment temperature of the second separation process S33, that isthe temperature of the aqueous solution including the solvent, is notparticularly limited as long as the dissolving of the adhesive agentproceeds and the configurational materials of the used hygiene productsare disassembled. The treatment temperature may be room temperature, ormay be higher than the room temperature, and for example, 15 to 30° C.may be mentioned. Further, the treatment time of the second separationprocess S33, that is, the time during which the top sheets, the backsheets and the absorbent bodies are immersed in the aqueous solutionincluding the solvent, is not particularly limited as long as thedissolving of the adhesive agent proceeds and the configurationalmaterials of the used hygiene products are disassembled. As thetreatment time, for example, 2 to 60 minutes may be mentioned, andpreferably the treatment time is 5 to 30 minutes. Still further, theamount of the aqueous solution in the second separation process S33,that is, the amount of the aqueous solution including the solvent, isnot particularly limited as long as the dissolving of the adhesive agentproceeds and the configurational materials of the used hygiene productsare disassembled. The amount of the aqueous solution may be, forexample, with respect to 100 parts by mass of the used hygiene products,preferably 300 to 3000 parts by mass, and more preferably 500 to 2500parts by mass. By the second separation process S33, the amount of theadhesive agent which remains in the films, the nonwoven fabric, theabsorbent bodies, etc., can be brought to be 1 mass % or lower withrespect to the films, the nonwoven fabric, the absorbent bodies, etc.

Incidentally, in the present embodiment, as another preferable aspect,the above-mentioned second separation process S33 can be also performedin the above-mentioned inactivation process S31. That is, whileinactivating the super absorbent polymers which are attached to the topsheets, the back sheets and the pulp fibers, the adhesive agent which isattached to the top sheets, the back sheets and the pulp fibers may bedissolved. In this case, as the aqueous solution in which the topsheets, the back sheets, the pulp fibers, and the super absorbentpolymers are immersed, an aqueous solution which includes both of theinactivation agent and a solvent is used. Accordingly, in theabove-mentioned inactivation process S31, the back sheets (the films),the top sheets (the nonwoven fabric), and the absorbent bodies (the pulpfibers and the super absorbent polymers) can brought to be in a state ofbeing generally separated in the aqueous solution. Then, in thesubsequent first separation process, the back sheets (the films), thetop sheets (the nonwoven fabric), the absorbent bodies (the pulp fibersand the super absorbent polymers) can be separated from one another, andthe second separation process S33 can be omitted. In this case, the backsheets (the films) and the top sheets (the nonwoven fabric) aresubstantially separated from each other by the removal of the adhesiveagent.

In the present embodiment, the separation process S13 may furtherinclude the first drying process S34, subsequent to the process ofremoving the adhesive agent in the joining portion, of drying the filmsin an atmosphere with a temperature higher than the room temperature orby hot air so as to remove the solvent. In the present embodiment, thenonwoven fabric is also dried in this process.

In reusing used hygiene products, the sterilization is very important.In the first drying process S34, the process of drying the separatedfilms (the back sheets) and the nonwoven fabric (the top sheets) in anatmosphere with a high temperature or by hot air is performed. Thedrying temperature is, for example, 105 to 210° C., and is preferably110 to 190° C. The drying time is, although depending on the dryingtemperature, for example, 10 to 120 minutes, and is preferably 15 to 100minutes. Accordingly, not only the solvent which remains on the surfacesof the films and the nonwoven fabric is evaporated and removed, but alsothe films and the nonwoven fabric can be sterilized by the atmospherewith a high temperature or hot air, etc. Thus, it becomes possible toexhibit an effect of the sterilization (the disinfection) while removingthe solvent.

On the other hand, in the present embodiment, the separation process S13may include the third separation process S35 of separating the pulpfibers from the separated mixture. In the third separation process S35,the method of separating the pulp fibers from the separated mixture(which includes the pulp fibers, the super absorbent polymers, and thewaste water) is not particularly limited, and for example, the separatedmixture is discharged while being let to pass through a screen withopenings of 0.1 to 4 mm, and preferably of 0.15 to 2 mm. Accordingly,the super absorbent polymers and the waste water are brought into thedischarged water, while the pulp fibers (in which the super absorbentpolymers remain mainly on the surface thereof) remain on the screen,whereby the pulp fibers can be separated from the mixture. Although suchpulp fibers include a large amount of impurities, the pulp fibers can bereused in this state depending on the application.

In the separated pulp fibers, the super absorbent polymers are attached,and the separated pulp fibers and the super absorbent polymers attachedto the pulp fibers are mixed with water by a predetermined ratio,whereby proceed to the ozone treatment process S36 as a liquid mixture.

In the present embodiment, the separation process S13 includes the ozonetreatment process S36 of treating the liquid mixture which includes thesuper absorbent polymers and the pulp fibers, the connected structurethereof, and water, by an aqueous solution including ozone, wherebylowers the molecular weight of the super absorbent polymers attached tothe pulp fibers, and solubilizes and removes the same.

In used hygiene products, in absorbent bodies, etc., which include pulpfibers and super absorbent polymers, (i) as the super absorbent polymersabsorb liquid, such as body fluid, etc., the super absorbent polymersenlarge and drag in the pulp fibers, and (ii) the enlarged superabsorbent polymers cause gel blocking, etc., while dragging in the pulpfibers, whereby there are many cases in which a plurality of superabsorbent polymers and a plurality of pulp fibers form a connectedstructure. In the above-mentioned liquid mixture, in addition to thefree pulp fibers and the free super absorbent polymers, the connectedstructure which is configured by a plurality of super absorbent polymersand a plurality of pulp fibers is included.

In the ozone treatment process S36, the super absorbent polymers whichare included in the liquid mixture (the treatment liquid) areoxidatively decomposed by ozone in the aqueous solution so as to besolubilized in the aqueous solution, whereby are removed.

The state in which the super absorbent polymers are oxidativelydecomposed and are solubilized in an aqueous solution is a state inwhich the super absorbent polymers and the connected structure passthrough a screen with openings of 2 mm. Accordingly, the impurities suchas the super absorbent polymers, etc., can be removed from the liquidmixture (the treatment liquid) and the pulp fibers with high purity canbe generated. Further, by the ozone treatment, the secondarysterilization, the bleach, and the deodorization of the pulp fibers canbe performed.

FIG. 2 is a schematic view which shows one example of the configurationof the apparatus 2 that performs the ozone treatment process S36. Theapparatus 2 includes the liquid mixture storage portion 3 which storesthe liquid mixture 51 that includes water, the pulp fibers and the superabsorbent polymers which have been separated in the third separationprocess S35, and the ozone treatment portion 4 which oxidativelydecomposes the super absorbent polymers included in the liquid mixture51 so as to remove the same from the pulp fibers.

The liquid mixture storage portion 3 includes the liquid mixture tank 12and the stirring machine 13. The liquid mixture tank 12 stores theliquid mixture 51 which is supplied through the pipe 61. The stirringmachine 13 stirs the liquid mixture 51 in the liquid mixture tank 12 sothat the pulp fibers and the super absorbent polymers in the liquidmixture 51 are not separated from water and do not sink downward in theliquid mixture 51.

On the other hand, the ozone treatment portion 4 includes the supplypump 21, the treatment tank 31, the ozone supply apparatus 41, thedelivery pump 22, and the ozone decomposition apparatus 34. Thetreatment tank 31 includes an acidic aqueous solution as the treatmentliquid 52. The treatment tank 31 includes the liquid mixture supply port32, the treatment liquid discharge port 33, and the ozone containing gassupply port 43. The liquid mixture supply port 32 is arranged on theupper portion of the treatment tank 31, and supplies the liquid mixture51 to the treatment tank 31. The treatment liquid discharge port 33 isarranged on the lower portion of the treatment tank 31, and dischargesthe treatment liquid 52. The ozone containing gas supply port 43 isarranged on the lower portion of the treatment tank 31, and morespecifically is arranged on the upper portion compared to the treatmentliquid discharge port 33, and delivers the ozone containing gas 53 intothe treatment tank 31.

More specifically, the supply pump 21 supplies continuously the liquidmixture 51 in the liquid mixture tank 12 through the pipe 62 from theliquid mixture supply port 32 into the treatment tank 31 in the firstflow rate. The ozone supply apparatus 41 supplies the ozone containinggas 53 into the treatment tank 31. As the ozone generation apparatus 42of the ozone supply apparatus 41, for example, the ozone water exposuretester ED-OWX-2 manufactured by EcoDesign, Inc., the ozone generationapparatus OS-25V manufactured by Mitusbishi Electric Corporation, etc.,may be mentioned. The ozone containing gas 53 is a gas of differenttypes of gas including ozone, and for example, an oxygen gas includingozone may be mentioned. The ozone containing gas supply port 43 deliversthe ozone containing gas 53 which is supplied to the treatment tank 31through the pipe 65 into the treatment tank 31, and is arranged on thelower portion (preferably at the bottom portion) of the treatment tank31. The ozone containing gas supply port 43 supplies continuously theozone containing gas 53 into the treatment liquid 52 from the lowerportion toward the upper portion of the treatment liquid 52 (thetreatment tank 31) as a plurality of fine bubbles. The delivery pump 22discharges continuously the treatment liquid 52 inside the treatmenttank 31 through the pipe 63 from the treatment liquid discharge port 33to the outside of the treatment tank 31 in the second flow rate. Theozone decomposition apparatus 34 receives the ozone containing gas 53which is accumulated at the upper portion of the treatment tank 31through the pipe 64, detoxifies the ozone and releases the detoxifiedozone to the outside. Incidentally, the treatment liquid 52 inside thetreatment tank 31 is only the treatment liquid 52 before the initiationof the ozone treatment process S36, and after the initiation thereof, isto be the liquid in which the treatment liquid 52 and the liquid mixture51 are mixed, however, in the present embodiment, the liquid inside thetreatment tank 31 including the liquid in which the treatment liquid 52and the liquid mixture 51 are mixed is altogether regarded as thetreatment liquid 52.

Subsequently, the specific method of the ozone treatment process S36 isexplained.

The pulp fibers and the super absorbent polymers which have beenseparated in the third separation process S35 are mixed with water so asto have a previously set concentration, whereby is to be the liquidmixture 51. The concentration of the pulp fibers in the liquid mixture51 is set so as to have a previously set concentration in a state inwhich the pulp fibers are thrown into the treatment tank 31 and aremixed with the treatment liquid 52. The liquid mixture 51 is supplied tothe liquid mixture tank 12 through the pipe 61, and is stored therein.Since the specific gravity of the pulp fibers and the super absorbentpolymers is larger than 1, the liquid mixture 51 is stirred inside theliquid mixture tank 12 by the stirring machine 13 so that the pulpfibers and the super absorbent polymers do not separate with water.

Further, the liquid mixture 51 inside the liquid mixture tank 12 iscontrolled with the flow rate by the supply pump 21, and is suppliedcontinuously through the pipe 62 from the liquid mixture supply port 32to the treatment tank 31 in the first flow rate. The treatment liquid 52is an acidic aqueous solution, and the specific gravity thereof isapproximately 1. Accordingly, the pulp fibers and the super absorbentpolymers sink from the upper portion to the lower portion of thetreatment liquid 52.

On the other hand, the ozone containing gas 53 which is generated by theozone generation apparatus 42 is supplied to the treatment tank 31through the pipe 65, and is released from the ozone containing gassupply port 43 of the treatment tank 31 into the treatment liquid 52 ina state of fine bubbles (for example, as microbubbles or nanobubbles).That is, the ozone containing gas 53 rise from the lower portion towardthe upper portion of the treatment liquid 52.

Further, the pulp fibers and the super absorbent polymers which moveinside the treatment liquid 52 toward the lower portion, that is, whichare lowered, and the ozone containing gas 53 which moves toward above,that is which rises, collide with each other while proceeding withfacing each other. Further, the ozone containing gas 53 is attached tothe surfaces of the pulp fibers, the super absorbent polymers, and theconnected structure. The ozone in the ozone containing gas 53oxidatively decomposes the free super absorbent polymers, and dissolvesthe same in the treatment liquid 52. Accordingly, the super absorbentpolymers on the pulp fibers are removed from the pulp fibers. Further,the pulp fibers are lowered toward the bottom portion of the treatmenttank 31, and the ozone containing gas 53 exits to the space in the upperportion of the treatment tank 31.

Among the free super absorbent polymers, the free pulp fibers, and theconnected structure, the free super absorbent polymers and the connectedstructure including the super absorbent polymers which have relativelyhigher specific gravity tend to have higher sedimentation than the freepulp fibers which have relatively lower specific gravity. On the otherhand, since the ozone containing gas consumes ozone and rises whiletreating the super absorbent polymers and the pulp fibers, the ozonecontaining gas which is present in a lower position tends to have higherozone content ratio (that is, being fresher) than the ozone containinggas which is present in an upper position.

Accordingly, the free super absorbent polymers and the connectedstructure, the movement toward the lower position of which is relativelyfast, can be properly oxidatively decomposed by a fresher ozonecontaining gas, whereby free pulp fibers can be formed. On the otherhand, since the movement toward the lower position of the free pulpfibers is relatively slow, the ozone containing gas can treat the freepulp fibers (and the pulp fibers for saccharification to be formed) bytaking time. To be more specific, ozone in the ozone containing gascollides with the pulp fibers while facing the same, whereby lignin ofthe pulp fibers (and the pulp fibers for saccharification) can bedecomposed.

Subsequently, the treatment liquid 52 (including the pulp fibers forsaccharification) in the bottom portion of the treatment tank 31 isdischarged continuously from the treatment liquid discharge port 33 ofthe treatment tank 31 to the outside of the treatment tank 31 in thesecond flow rate through the pipe 63 by the flow rate control of thedelivery pump 22. The ozone in the ozone containing gas 53 which isaccumulated at the upper portion of the treatment tank 31 is detoxifiedby the ozone decomposition apparatus 34, and is released to the outside.

In this manner, the liquid mixture 51 is supplied continuously from theupper portion of the treatment tank 31 into the treatment tank 31 in thefirst flow rate, and the treatment liquid 52 is discharged continuouslyfrom the lower portion (the bottom portion) of the treatment tank 31 tothe outside of the treatment tank 31 in the second flow rate.Accordingly, a continuous and stable flow of fluid (including the pulpfibers) from the upper portion toward the lower portion inside thetreatment tank 31 can be forcibly caused.

The treatment liquid 52 which is to be discharged from the treatmenttank 31 includes the pulp fibers for saccharification from which thesuper absorbent polymers are removed, and further includes organicmatter with low molecular weight which is generated by the superabsorbent polymers being oxidatively decomposed. The pulp fibers forsaccharification is recovered in the process which is further downstreamof the delivery pump 22, for example, in the fourth separation processS37 which will be described later.

The present method at least, while supplying continuously the liquidmixture 51 which includes the pulp fibers and the super absorbentpolymers into the treatment tank 31 which includes the treatment liquid52 capable of dissolving the super absorbent polymers in the first flowrate, discharges continuously the treatment liquid 52 which includes thepulp fibers for saccharification from which the super absorbent polymersare removed, and further includes organic matter with low molecularweight which is generated by the super absorbent polymers beingoxidatively decomposed, to the outside of the treatment tank 31 in thesecond flow rate. By having such a configuration, a continuous andstable flow of fluid (including the pulp fibers) from the liquid mixturesupply port 32 which supplies the liquid mixture 51 in the treatmenttank 31 toward the treatment liquid discharge port 33 which dischargesthe treatment liquid 52 can be forcibly caused. By the flow of fluid,that is, by the water stream, even when the treatment amount of the pulpfibers and the super absorbent polymers is increased, the superabsorbent polymers can be treated (solubilized) and the pulp fibers canbe treated.

The first flow rate and the second flow rate are preferably the same. Bysetting the first flow rate and the second flow rate the same, theamount of the treatment liquid 52 inside the treatment tank 31 can bemaintained constant, and the treatment can be performed stably andcontinuously. Note that when the amount of the treatment liquid 52inside the treatment tank 31 can be maintained approximately constant,that is, if the amount of the treatment liquid 52 inside the treatmenttank 31 does not largely increase or decrease, the first flow rate andthe second flow rate may vary over time. That is, the first flow rateand the second flow rate do not necessarily have to be completely thesame at all times, and may be approximately the same on average overtime. Note that “approximately the same” is referred to as thedifference between the first flow rate and the second flow rate beingwithin 5 mass % or less. Also in such a case, the treatment can beperformed stably and continuously.

In a case in which the ozone containing gas 53 is supplied to thetreatment liquid 52, the ozone concentration in the treatment liquid 52is not particularly limited as long as the ozone can oxidativelydecompose the super absorbent polymers, and for example, 1 to 50 massppm may be mentioned, and the ozone concentration is preferably 2 to 40mass ppm, and more preferably 3 to 30 mass ppm. When the ozoneconcentration in the treatment liquid 52 is too low, the super absorbentpolymers may not be completely solubilized, and the super absorbentpolymers may remain in the pulp fibers. Conversely, when the ozoneconcentration in the treatment liquid 52 is too high, since theoxidizing power also increases, the pulp fibers may be damaged, andfurther, it is possible that safety issues may be caused. The ozonetreatment temperature is not particularly limited as long as the superabsorbent polymers can be oxidatively decomposed, and for example, thetemperature may be kept in room temperature, or may be set to atemperature higher than the room temperature.

The concentration of ozone in the treatment liquid 52 (the aqueoussolution) is measured by the following method.

(1) In a 100 mL graduated cylinder containing approximately 0.15 g ofpotassium iodide and 5 ml of 10% citric acid solution, 85 mL of thetreatment liquid 52 in which ozone is dissolved is added and reacted.

(2) The treatment liquid 52 after reaction is moved to 200 mL Erlenmeyerflask, a starch solution is added to the Erlenmeyer flask, and iscolored to purple, and thereafter, titration is performed while stirringthe mixture until the mixture become colorless by 0.01 mol/L of sodiumthiosulfate, and the addition amount a (mL) is recorded.

(3) The concentration of ozone in the aqueous solution is calculated byusing the following formula.

The concentration of ozone in the aqueous solution (mass ppm) iscalculated by the following formula:

The concentration of ozone in the aqueous solution (mass ppm)=a(mL)×0.24×0.85 (mL)

The ozone concentration in the ozone containing gas 53 is preferably 40to 200 g/m³, more preferably 40 to 150 g/m³, and even more preferably 40to 100 g/m³. When the ozone concentration in the ozone containing gas 53is too low, the super absorbent polymers may not be completelysolubilized, and the super absorbent polymers may remain. When the ozoneconcentration in the ozone containing gas 53 is too high, the pulpfibers may be damaged, safety may be reduced, and the manufacturingcosts may increase. Incidentally, the ozone concentration in the ozonecontaining gas 53 may be measured, for example, by a UV absorption typeozone concentration meter (for example, ozone monitor OZM-5000Gmanufactured by EcoDesign, Inc.).

The concentration of the pulp fibers and the super absorbent polymers inthe treatment liquid 52 is not particularly limited as long as the superabsorbent polymers can be oxidatively decomposed by the ozone in thetreatment liquid 52, and for example, 0.1 to 20 mass % may be mentioned,and the concentration thereof is preferably 0.2 to 10 mass %, and ismore preferably 0.3 to 5 mass %. When the concentration of the pulpfibers is too high, the super absorbent polymers may not be completelysolubilized, and the super absorbent polymers may remain in the pulpfibers. Conversely, when the concentration of the pulp fibers is toolow, since the oxidizing power also increases, the pulp fibers may bedamaged, and further, it is possible that safety issues may be caused.The concentration of the pulp fibers and the super absorbent polymers inthe liquid mixture 51 is appropriately set based on the above-mentionedconcentration of the pulp fibers and the super absorbent polymers in thetreatment liquid 52 and the amount of the treatment liquid 52.

In a case in which ozone is supplied to the treatment liquid 52 whichincludes the pulp fibers and the super absorbent polymers, the treatmentliquid 52 is preferably acidic. More preferably, pH of the treatmentliquid 52 is higher than 0 and is 5.0 or lower, and even morepreferably, is 1.5 to 2.5. By being treated in an acidic state, theinactivation of ozone is suppressed, the oxidative decomposition effectfor the super absorbent polymers by ozone is improved, whereby the superabsorbent polymers can be oxidatively decomposed in a short amount oftime. In order to maintain pH of the treatment liquid, pH of the liquidmixture 51 may be set to the same as that of the treatment liquid 52,and the liquid mixture 51 may be supplied to the treatment tank 31.Alternatively, pH of the treatment liquid 52 may be monitored by a pHsensor, and when pH is varied to the neutral side, a predeterminedacidic aqueous solution may be added to the treatment liquid 52 by theamount in accordance with the varied range.

The amount of the treatment liquid 52 (including the liquid mixture 51)inside the treatment tank 31 is not particularly limited as long as itcan oxidatively decompose the super absorbent polymers, although it ispreferable that the volume V (unit: L) of the treatment liquid 52 insidethe treatment tank 31 and the mass W (unit: kg) of the pulp fiberssatisfy 30≤V/W≤1000. It is more preferable that they satisfy 50≤V/W≤400,and even more preferable that they satisfy 100≤V/W≤200. When V/W is toosmall, the super absorbent polymers may not be completely solubilized,and the super absorbent polymers may remain. When V/W is too large, themanufacturing costs may increase. Incidentally, the volume V of thetreatment tank 31 is not particularly limited, and for example, 50 to 80L may be mentioned.

It is preferable that the flow rate R_(O) (unit: L/minute) of the ozonecontaining gas and the volume V (unit: L) of the treatment liquid 52inside the treatment tank 31 satisfy 0.01≤R_(O)/V≤1.25. It is morepreferable that they satisfy 0.03≤R_(O)/V≤1.0, and even more preferablethat they satisfy 0.06≤R_(O)/V≤0.75. When R_(O)/V is too small, thesuper absorbent polymers may not be completely solubilized, and thesuper absorbent polymers may remain in the pulp fibers. When R_(O)/V istoo large, the pulp fibers may be damaged, safety may be reduced, andthe manufacturing costs may increase. Incidentally, the flow rate R_(O)of the ozone containing gas is not particularly limited, and forexample, 3 to 6 L/minute may be mentioned.

The time during which the pulp fibers are present inside the treatmenttank 31, that is, the time during which the pulp fibers are treated inthe treatment liquid 52 (hereinbelow, which may also be referred to as“the in-tank treatment time”) is not particularly limited as long assuch time can oxidatively decompose the super absorbent polymers. Thein-tank treatment time may be short when the ozone concentration of thetreatment liquid 52 is high, and it takes a long time when the ozoneconcentration of the treatment liquid 52 is low. As the in-tanktreatment time, for example, 2 to 60 minutes may be mentioned, and thein-tank treatment time is preferably 5 to 30 minutes. The product(hereinbelow, which may also be referred to as “the CT value”) of ozoneconcentration (mass ppm) in the treatment liquid 52 and the in-tanktreatment time (minute) is preferably 100 to 6000 ppm·minute, is morepreferably 200 to 4000 ppm·minute, and is even more preferably 300 to2000 ppm·minute. When the CT value is too small, the super absorbentpolymers may not be completely solubilized, and the super absorbentpolymers may remain in the recovered pulp fibers. When the CT value istoo large, the pulp fibers may be damaged, safety may be reduced, andthe manufacturing costs may increase.

While the pulp fibers are present inside the treatment tank 31, thesuper absorbent polymers are oxidatively decomposed into components withlow molecular weight by ozone, and are dissolved in the treatment liquid52. The components with low molecular weight which are dissolved in thetreatment liquid 52 are discharged together with the treatment liquid52. Further, in this process, by the sterilization action of ozone, theused hygiene products are subjected to primary disinfection.

In the present embodiment, as a preferred aspect, the ozone treatmentprocess S36 (the continuous treatment process) includes the process ofwhile supplying continuously the liquid mixture 51 from the upperportion of the treatment tank 31, discharging continuously the treatmentliquid 52 from the lower portion of the treatment tank 31. Since thespecific gravities of the pulp fibers and the super absorbent polymersin the liquid mixture 51 are larger than the specific gravity of waterin the treatment liquid 52, the pulp fibers, the super absorbentpolymers, and the connected structure naturally sink.

In the present embodiment, as a preferred aspect, the treatment liquid52 which is capable of dissolving the super absorbent polymers is anaqueous solution which includes the ozone containing gas whichoxidatively decomposes the super absorbent polymers so that they can bedissolved. The ozone treatment process S36 (the continuous treatmentprocess) further includes the delivery process of deliveringcontinuously a plurality of bubbles of the ozone containing gas from thelower portion toward the upper portion of the treatment liquid 52. Insuch a preferred aspect of the present method, in the treatment liquid52, the ozone containing gas is raised and the pulp fibers and the superabsorbent polymers are lowered, that is, they form an opposed flow.Accordingly, the possibility of the pulp fibers and the super absorbentpolymers coming into contact with the ozone containing gas can beincreased. Further, the deeper the pulp fibers and the super absorbentpolymers sink, the higher the concentration of the ozone containing gasthe pulp fibers and the super absorbent polymers can come into contactwith. Accordingly, the super absorbent polymers which could not havesufficiently been dissolved in the treatment liquid 52 only by the ozonecontaining gas with which the super absorbent polymers came into contactat the shallow portion in the treatment liquid 52, can be made to comeinto contact with the ozone containing gas with a high concentration atthe deep portion in the treatment liquid 52. Thus, the super absorbentpolymers can be reliably dissolved into the treatment liquid 52.Therefore, the super absorbent polymers can be reliably dissolved intothe treatment liquid, whereby can be removed from the fibers.

In the present embodiment, as a preferred aspect, the above-mentioneddelivery process includes the process of delivering the ozone containinggas in a state of microbubbles or nanobubbles. Note that microbubblesare bubbles with diameter of approximately 1 to 1000 μm, and preferably10 to 500 μm, and nanobubbles are bubbles with diameter of approximately100 to 1000 nm, and preferably 100 to 500 nm. The microbubbles ornanobubbles are such fine bubbles, and have a property that the surfacearea per unit volume is large and the rising speed in liquid is slow.Accordingly, in the present method, as a preferred aspect, such finebubbles of ozone containing gas are delivered from the lower portiontoward the upper portion of the treatment liquid 52 in the treatmenttank 31.

On the other hand, the pulp fibers and the super absorbent polymers movefrom the upper portion toward the lower portion. At this time, since thefine bubbles have slow rising speed, the possibility that the bubblescome into contact with the pulp fibers can be increased. Further, sincethe occupation area of the fine bubbles in the surface of the pulpfibers is small, more bubbles can be made to come into contact with thesurface of the pulp fibers. Accordingly, the pulp fibers, the superabsorbent polymers, and the connected structure can be evenly wrappedwith fine bubbles, and the contact area of these and the ozonecontaining gas can be further increased. Still further, more bubblescome into contact with the surface of the pulp fibers, whereby thesedimentations of the pulp fibers, the super absorbent polymers, and theconnected structure are reduced by the buoyant force of bubbles, and thetime during which these and the ozone containing gas that come intocontact with can be increased. Thus, the super absorbent polymers can bereliably dissolved into the treatment liquid 52, whereby can be removedfrom the pulp fibers.

In the present embodiment, as a preferred aspect, the treatment liquid52 is an acidic aqueous solution, and for example, is an acidic aqueoussolution with pH of 2.5 or lower. In this case, even when the absorptioncapacity of the super absorbent polymers in the liquid mixture 51partially remains, the absorption and swelling of the super absorbentpolymers can be suppressed. Accordingly, the super absorbent polymerscan be dissolved into the treatment liquid 52 in a short amount of time,and the super absorbent polymers can be more reliably moved. Especially,in a case in which the treatment liquid 52 is an ozone containingaqueous solution, ozone in the ozone containing aqueous solution can bemade so that it is difficult to be inactivated, whereby the superabsorbent polymers can be dissolved in a shorter amount of time so as tobe dissolved, and the super absorbent polymers can be more reliablyremoved from the fibers.

Further, as another preferred embodiment, the configuration of thetreatment tank 31 can be a configuration other than that shown in FIG.2. FIG. 3 is a schematic view which shows another configurationalexample of the apparatus 2 of the ozone treatment process of FIG. 1. Theapparatus 2 shown in FIG. 3 is different from the apparatus 2 shown inFIG. 2 in that the pipe 63 of the ozone treatment portion 4 has acontinuous U-shaped pipe structure in which two U-shaped pipes areconnected reversely and continuously to each other, and the deliverypump 22 is omitted. In such a case, when the pipe 63 is filled with thetreatment liquid 52, and the height of the liquid surface of thetreatment liquid 52 inside the treatment tank 31 is higher than theheight of the liquid surface of the liquid inside the tank of thesubsequent process connected by the pipe 63, the treatment liquid 52 isdischarged to the tank of the subsequent process through the pipe 63, bythe principle of siphon. Accordingly, before initiation of the process,by initially setting the height of the liquid surface of the treatmentliquid 52 inside the treatment tank 31 the same as the height of theliquid surface of the liquid inside the tank of the subsequent process,and by the initiation of the process, when the liquid mixture 51 issupplied continuously into the treatment tank 31 in the first flow rate,the treatment liquid 52 is to be discharged to the tank of thesubsequent process through the pipe 63 so as to satisfy “second flowrate=first flow rate”, by the principle of siphon. Note that the heightof the liquid surface of the liquid inside the tank of the subsequentprocess is to maintain the height before the initiation of the processeven during the process. In this case, the delivery pump 22 is notnecessary, and the control of the second flow rate of the delivery pump22 is no longer necessary.

In the present embodiment, the separation process S13 may furtherinclude the fourth separation process S37 of separating the pulp fibersfrom the treatment liquid 52 which is discharged from the treatment tank31, and the second drying process S38 of drying the separated pulpfibers.

In the fourth separation process S37, the method of separating the pulpfibers from the treatment liquid 52 which is discharged from thetreatment tank 31 is not particularly limited, and for example, themethod of letting the treatment liquid 52 including the pulp fibers forsaccharification pass through, for example, a screen mesh with openingsof 0.15 to 2 mm, may be mentioned. When the treatment liquid 52including the pulp fibers for saccharification is made to pass through ascreen mesh with openings of 0.15 to 2 mm, the waste water including theproducts by the oxidative decomposition of the super absorbent polymerspasses through the screen. On the other hand, the pulp fibers forsaccharification remain on the screen.

In the subsequent second drying process S38, the separated pulp fibersare dried in an atmosphere with a high temperature or by hot air, etc.The drying temperature is, for example, 105 to 210° C., and ispreferably 110 to 190° C. The drying time is, although depending on thedrying temperature, for example, 10 to 120 minutes, and is preferably 15to 100 minutes. Accordingly, the solvent which remains on the surfacesof the pulp fibers is evaporated and removed, whereby pulp fibers inwhich mixed ratio of super absorbent polymers is extremely low and withhigh purity can be recovered. Thus, the configurational materials of thehygiene products can be efficiently recovered. Further, the pulp fiberscan be sterilized (disinfected) by the atmosphere with a hightemperature or by hot air, etc.

In the present disclosure, the pulp fibers for saccharification have awater contact angle of 20° or less, and has a water contact anglepreferably of 15° or less, and more preferably of 10° or less.Accordingly, after the pulp fibers for saccharification which ismanufactured by the above-mentioned manufacturing method, is dried andstored, the pulp fibers for saccharification can be easily dispersed ina saccharification aqueous solution. Incidentally, from theabove-mentioned view point, the above-mentioned water contact angle ofthe pulp fibers for saccharification may be 0°.

The water contact angle of the pulp fibers for saccharification can bemeasured in the following manner.

(1) In a constant temperature and humidity chamber with a temperature of20±5° C. and a humidity of 65±5% RH, an aluminum ring (with an outerdiameter of 43 mm, an inner diameter of 40 mm, and a height of 5 mm) andthe pulp fibers for saccharification which have been dried at 120° C.for 60 minutes are prepared, and are left still for 24 hours.

(2) 1.5 g of the pulp fibers for saccharification is filled evenly inthe aluminum ring, and the pulp fibers for saccharification, togetherwith the aluminum ring, are compressed for 1 minute by a pressure of 3Mpa by using a pressing machine with a smooth bottom surface, wherebythe surface of the recycled pulp fibers is smoothed.

(3) The water contact angle of the compressed pulp fibers forsaccharification is measured in accordance with 6. Sessile drop methodof JIS R 3257: 1999 “Wetability test method for substrate glasssurface”. As the contact angle measuring apparatus, the automaticcontact angle measurer CA-V type manufactured by Kyowa InterfaceScience, Inc., may be mentioned. The above-mentioned water contact anglemeans the value after 200 ms, after dropping deionized water.

(4) The water contact angles are measured for 20 different samples, andthe average value thereof is adopted.

In the present disclosure, the pulp fibers for saccharification have alignin content ratio of 0.1 mass % or less, and have a lignin contentratio preferably of 0.08 mass % or less, and more preferably of 0.06mass % or less. Accordingly, the pulp fibers for saccharification haveexcellent saccharification property.

The lignin content ratio of the pulp fibers for saccharification can bemeasured in accordance with the method described in pages 85 to 87 of“Soil diagnosis guidance” published in March, Showa 63, by Agriculture,forestry and fisheries department, Agriculture guidance division, ofEhime prefecture. Hereinbelow, the summary thereof is copied.

<Preparation of Reagents>

(1) In a constant temperature and humidity chamber with a temperature of20±5° C. and a humidity of 65±5% RH, the pulp fibers forsaccharification which have been dried at 120° C. for 60 minutes areprepared, and are left still for 24 hours.

(2) Commercially available lignin (95%) is prepared as a standardreagent.

(3) In a 500 mL beaker, 22.3 g of sodium pyrophosphate (Na₄P₂O₅.10H₂O)is measured, approximately 400 mL of deionized water is added and sodiumpyrophosphate is dissolved, whereby sodium pyrophosphate aqueoussolution is made.

(4) In another 500 mL beaker, 10 g of sodium hydroxide is measured,approximately 200 mL of deionized water is added and sodium hydroxide isdissolved, whereby sodium hydroxide aqueous solution is made.

The sodium pyrophosphate aqueous solution and the sodium hydroxideaqueous solution are made to cool down, are added to 1 L volumetricflask, are made to constant volume with deionized water, wherebypyrophosphate extract liquid is made.

<Previous Operation>

(5) 2 g of lignin is measured in 100 mL Erlenmeyer flask A.

(6) 2 g of the pulp fibers for saccharification is measured in another100 mL Erlenmeyer flask B.

(7) 20 mL of pyrophosphate extract liquid is added to each of Erlenmeyerflask A and Erlenmeyer flask B, and is shaken for 3 minutes.

(8) Erlenmeyer flask A and Erlenmeyer flask B are left still for 15minutes, and thereafter, are filtered with a filter paper No. 6, wherebylignin filtrate and pulp fibers for saccharification filtrate areobtained.

<Analysis>

(9) By using a whole pipette, 5 mL of lignin filtrate is added to 50 mLvolumetric flask, and is made to constant volume with deionized water(lignin 10,000 ppm).

(10) By using a measuring pipet, 1 mL, 2 mL, 5 mL and 10 mL of ligninfiltrate with constant volume is respectively added to four 100 mLvolumetric flasks, is made to constant volume with deionized water,whereby calibration solutions (100 ppm, 200 ppm, 500 ppm, and 1,000 ppm)are formed.

(11) Deionized water is set as blank, the transmittance of thecalibration solutions is measured at a wavelength of 530 nm, and isconverted to absorbance with reference to the absorbance conversiontable shown in page 235.

(12) The calibration curve between the concentration of the calibrationsolutions and the absorbance is created.

(13) The transmittance of the pulp fibers for saccharification filtrateis measured by setting deionized water as blank, is converted toabsorbance with reference to the absorbance conversion table shown inpage 235, and lignin concentration is calculated from the calibrationcurve.

(14) From the lignin concentration, the lignin content ratio (mass %) iscalculated.

Incidentally, the above-mentioned commercially available lignin (95%)may be changed to commercially available lignin (for example, lignin ofNacalai Tesque, Inc.) with different lignin concentration, etc.

In the manufacturing method of the present disclosure, the pulp fibersfor saccharification have a beating degree reduction speed preferably of300 mL or more, more preferably of 320 mL or more, still more preferablyof 340 mL or more, and even more preferably of 360 mL or more.Accordingly, in the subsequent saccharification step, it is easy for thepulp fibers for saccharification to fluff when being applied withphysical force, that is, to be increased in the surface area, wherebycan be easily saccharified.

Incidentally, the above-mentioned beating degree reduction speed can beobtained by the manufacturing method of the present disclosure achievingthe low lignin content ratio of the pulp fibers for saccharification,and the narrow distribution of the lignin content ratio, etc.

The above-mentioned beating degree reduction speed is measured inaccordance with the following beating degree reduction test.

<Beating Degree Reduction Test>

(1) The pulp fibers for saccharification are beaten for one hour orlonger, preferably for two hours, in accordance with Pulp—Beatingmethod—Part 1: Beater method of JIS P 8221-1: 1998.

(2) After initiation of the beating, samples are taken every 20 minutes,and the beating degree (Canadian Standard freeness) of each sample ismeasured in accordance with Pulp—Freeness test method—Part 2: CanadianStandard freeness method of JIS P 8121-2:2012. Note that the test may bestopped when the beating degree of the samples is lower than 100 mL.

(3) Time (h) is plotted on the horizontal axis, and the beating degree(mL) is plotted on the vertical axis, so as to approximate the plots toa linear function by using the least square method, and the absolutevalue of the slope thereof is adopted as the beating degree reductionspeed (mL/m).

Incidentally, the larger the value of the beating degree reductionspeed, the reduction of the beating degree per unit time is fast, thatis, meaning that it is easier for the pulp fibers for saccharificationto be beaten (to fluff).

In the present disclosure, the pulp fibers for saccharification have anash content ratio preferably of 0.65 mass % or less, more preferably of0.50 mass % or less, still more preferably of 0.30 mass % or less, andeven more preferably of 0.20 mass % or less. Accordingly, in a case inwhich the saccharification step is performed, for example, under thepresence of a cellulase enzyme, it is difficult for the activity of thecellulase enzyme to be inhibited by metal ions.

The above-mentioned ash content ratio can be reduced by selecting, inthe inactivation process S31 of inactivating the super absorbentpolymers, an acid which can form a complex with metal ions included inan excrement, and especially citric acid, as the inactivation agent.

In the present description, ash means the amount of inorganic ornon-flammable residue left after organics have been ashed, and ashcontent ratio means the ratio (mass ratio) of ash included in materialsto be promoted. The above-mentioned ash content ratio is measured inaccordance with “5. Ash test method” of “2. General test method” inPhysiological treatment material standard. To be more specific, the ashcontent ratio is measured as follows.

(1) A platinum, quartz, or magnetic crucible is preheated at strong heatof 500 to 550° C. for 1 hour, allow the same to cool down, and the massthereof is measured precisely.

(2) 2 to 4 g of the pulp fibers for saccharification which have beendried at 120° C. for 60 minutes is taken, is added into the crucible,the mass thereof is measured precisely, the lid of the crucible isremoved or shifted if necessary, and while weakly heated initially, thetemperature is gradually increased up to strong heat of 500 to 550° C.for more than 4 hours, so as to be ashed until no carbide remains.

(3) After allowing the same to cool down, the mass thereof is measuredprecisely. The residue is ashed again until the same reaches a constantweight, after allowing the same to cool down, the mass thereof ismeasured precisely, and the measured mass is regarded as the ash contentratio (mass %).

In the present embodiment, as a preferred aspect, before the ozonetreatment process S36 (the continuous treatment process), theinactivation process S31 of, treating the mixture by using an aqueoussolution which can inactivate the absorption capacity of the superabsorbent polymers, whereby inactivating the absorption capacity of thesuper absorbent polymers in the mixture, and before the ozone treatmentprocess S36 (the continuous treatment process), the first separationprocess S32 of separating the inactivated super absorbent polymers andthe pulp fibers from the aqueous solution, are further included. In sucha manner, in the present method, as a preferred aspect, in theinactivation process S31, the absorption capacity of the super absorbentpolymers is suppressed by an aqueous solution which can inactivate theabsorption capacity of the super absorbent polymers, whereby at thestage of the ozone treatment process S36 (the continuous treatmentprocess) in the subsequent process, the super absorbent polymers can bedissolved more easily and in a shorter amount of time by the treatmentliquid 52.

In the present embodiment, as a preferred aspect, in the inactivationprocess S31, the aqueous solution which can inactivate the absorptioncapacity of the super absorbent polymers is an acidic aqueous solution,and for example, is an acidic aqueous solution with pH of 2.5 or lower.In this manner, in the present method, as a preferred aspect, theaqueous solution which can inactivate the absorption capacity of thesuper absorbent polymers is an acidic aqueous solution, whereby thesuper absorbent polymers can be more easily inactivated, and at thestage of the inactivation process S31, the absorption capacity of thesuper absorbent polymers can be more reliably suppressed. Accordingly,at the stage of the ozone treatment process S36 (the continuoustreatment process) in the subsequent process, the super absorbentpolymers can be dissolved more easily and in a shorter amount of time bythe treatment liquid.

Further, as another preferred embodiment, the treatment tank 31 mayinclude the first treatment tank 31-1 and the second treatment tank 31-2which are at least connected to each other in series. FIG. 4 is aschematic view which shows still another configurational example of theapparatus 2 of the ozone treatment process of FIG. 1. The apparatus 2 ofFIG. 4 is different from the apparatus 2 of FIG. 2 in that two ozonetreatment portions 4 are joined in series, in other words, the firsttreatment tank 31-1 and the second treatment tank 31-2 are joined inseries. In such a case, for example, the liquid mixture 51 is treated inmultiple stages, such that the first treatment tank 31-1 is suppliedwith the liquid mixture 51 and discharges the first treated liquid (thetreatment liquid 52-1 in the first treatment tank 31-1), and the secondtreatment tank 31-2 is supplied with the first treated liquid anddischarges the second treated liquid (the treatment liquid 52-2 in thesecond treatment tank 31-2). In such a case, in comparison to the caseof including one treatment tank 31 with large capacity, since treatmentis performed by the new treatment liquid 52-1, 52-2 for each of thefirst and the second treatment tanks 31-1, 31-2, for example, the superabsorbent polymers which could not be sufficiently dissolved in thefirst treatment tank (the treatment tank at the first stage) 31-1 can beeasily dissolved by the second treatment tank (the treatment tank at thenext stage) 31-2, etc., whereby the super absorbent polymers can be morereliably dissolved, and can be removed from the fibers.

In the present embodiment, as a preferred aspect, further in thematerial separation process Si, at the pretreatment process S11, theused hygiene products can be brought to the state of not being broken,etc., as they are, and of being extremely swollen by water without theinactivation of the super absorbent polymers. Accordingly, an extremelyhigh internal pressure is generated inside the used hygiene products,whereby the used hygiene products can be brought to a state in which anyportions of the surfaces are about to be torn. Then, in the disassemblyprocess S12, by applying physical impact on the used hygiene products insuch a state, any portions of the surfaces are torn, whereby theabsorbent core inside erupts outside. Therefore, the used hygieneproducts can be disassembled into at least the films (the back sheet),and the absorbent core. At this time, since the films substantiallymaintain the original shape, the films can be easily separated from theabsorbent core in the subsequent separation process S13. Accordingly,the configurational materials such as films, can be separated from otherconfigurational materials without being broken, etc., and maintainingthe shape as they are. Thus, the configurational materials such as filmsof the hygiene products can be recovered efficiently.

In the present embodiment, as a preferred aspect, by using terpene inremoving the adhesive agents, the hot melt adhesive agent which joinsthe configurational materials of the hygiene products can be dissolvedat a normal temperature. Accordingly, the hygiene products can be brokenapart easily and neatly, whereby the pulp fibers and the super absorbentpolymers are separated from the hygiene products, and the nonwovenfabric and films can be separated while maintaining individually thematerial form thereof. That is, the pulp fibers, the films, and thenonwoven fabric can be easily separately recovered without having tobreak the hygiene products and going through complicated separationprocesses. In a case in which limonene is used as terpene, as asecondary effect of limonene, since limonene has a refreshing citrussmell, the excrement-derived smell can be covered to a certain extent,and the burden of smell on workers and the adverse effects of smell inthe neighborhood, etc., can be reduced. Since limonene is monoterpeneand is similar in structure to styrene, limonene can dissolvestyrene-based hot melt adhesive agents which are generally used inhygiene products. Since cleaning treatment of hygiene products in thenormal temperature is possible, the energy cost can be reduced, andsmell generation and diffusion can be suppressed. Terpene has a highcleaning effect of oil stains, and other than the dissolving effect ofhot melt adhesive agents, in a case in which printing is provided in thefilms, the printing ink can also be decomposed and removed, whereby thefilms on which printing is provided can also be recovered as a plasticmaterial with high purity.

Further, when an organic acid aqueous solution with pH of 2.5 or loweris used for inactivation of the super absorbent polymers, it isdifficult to deteriorate the pulp fibers. Still further, when citricacid is used as the organic acid, by the chelating effect and thecleaning power of citric acid, removal effect of dirt components whichderive from excrement can be expected. Still further, disinfectioneffect and deodorizing effect on alkaline smell can also be expected.

Further, by oxidatively decomposing the super absorbent polymers byozone, it is possible to prevent contamination to the pulp fibers, andrapid increase of waste water by water absorption of the super absorbentpolymers, etc. By adjusting the concentration of ozone, it is possibleto perform oxidative decomposition of the super absorbent polymers andsterilization at the same time. Still further, in a case in which ozoneis used, since no chlorinated chemicals are used at all, RPF (refusederived paper and plastic fuel) with high quality which hardly damagescombustion furnace can be manufactured from the recovered plasticmaterials. Since salt is not used during the treatment process, saltdoes not remain in the pulp fibers, whereby pulp fibers forsaccharification with low ash and with high quality can be recovered.

The manufacturing method of the present disclosure may further includethe saccharification step of saccharifying the pulp fibers forsaccharification after the treatment liquid discharge step. As theabove-mentioned saccharification step, although not particularlylimited, saccharification methods known in the technical field areincluded. As the above-mentioned saccharification methods, for example,the methods described in Japanese Unexamined Patent Publication No.2006-141244, Japanese Unexamined Patent Publication No. 2009-183211,Japanese Unexamined Patent Publication No. 2010-17084, JapaneseUnexamined Patent Publication No. 2010-36058, and Japanese UnexaminedPatent Publication No. 2013-202021, etc., may be mentioned.

As the above-mentioned saccharification step, as shown in FIG. 1, thedried pulp fibers for saccharification which are obtained in the seconddrying process S38, or the undried pulp fibers for saccharificationwhich are obtained in the fourth separation process S37 may be subjectedto the saccharification step, or alternatively, the treatment liquid 52which includes the pulp fibers for saccharification that is obtained inthe ozone treatment process S36 may be subjected to the saccharificationstep.

EXAMPLES

The pulp fibers for saccharification were manufactured in accordancewith the method shown in FIG. 1 and FIG. 2, from a plurality of types ofused diapers which have been collected from a care facility. Theconditions related to the ozone treatment process S36 were as follows.

(i) liquid mixture 51

-   -   concentration: 1 mass % (concentration of the pulp fibers and        the super absorbent polymers)    -   pH: 2.4

(ii) treatment tank 31

-   -   capacity: 60 L    -   height: 2.6 m    -   first flow rate: 2 L/minute    -   second flow rate: 2 L/minute    -   in-tank treatment time: 30 minutes    -   V/W: 100    -   R_(O)/V: 0.033

(iii) ozone containing gas

-   -   ozone concentration: 100 g/m³    -   form: nanobubbles

Manufacturing Example 1

The inactivation process S31 was performed by using slaked lime, theozone treatment process S36 was performed under the above-mentionedconditions, and the obtained pulp fibers for saccharification were driedat 120° C. for 60 minutes, whereby the pulp fibers for saccharificationNo. 1 were obtained.

Comparative Manufacturing Example 1

In the same manner as the Manufacturing example 1 other than notdelivering the ozone containing gas in the ozone treatment process S36,the pulp fibers for saccharification No. 2 were obtained.

Comparative Manufacturing Example 2

NBKP virgin pulp fibers were set as the pulp fibers for saccharificationNo. 3.

Example 1, and Comparative Examples 1 and 2

The lignin content ratio (mass %), the water contact angle)(°, and theash content ratio (mass %) of the pulp fibers for saccharification No. 1to No. 3 were measured in accordance with the methods described in thepresent description. The results are shown in Table 1. Further, thebeating degree reduction speed (mL/h) of the pulp fibers forsaccharification No. 1 to No. 3, and the beating degree (mL) afterhaving been beaten for a predetermined amount of time in the beatingdegree reduction test were measured in accordance with the beatingdegree reduction test described in the present description. The resultsare also shown in Table 1.

The pulp fibers for saccharification No. 1 to No. 3 were subjected tosaccharification in accordance with the following cellulase method. Theresidual ratio (mass %) of the residue after saccharification is shownin Table 1.

<Cellulase Method>

(1) Approximately 3 g of the pulp fibers for saccharification wasweighed [mass: m₀ (g)], and thereafter, 160 mL of distilled water and 40mL of 0.5 M glycine-hydrochloric acid buffer (pH 4.0) were added, andfurther, 1 g of Cellulase Onozuka and 1 g of Cellulase Y-NC were added.

(2) The prepared sample was kept at 45° C., and was stirred for 3 hours.

(3) After treatment, the sample was neutralized with sodium hydrogencarbonate, and was added with calcium chloride.

(4) The supernatant was discarded, distilled water was added to theprecipitate to be stirred, and the supernatant was discarded. Thisoperation is repeated until the supernatant becomes transparent

(5) The precipitate was filtered with glass fiber filter paper, andthereafter was dried at 110° C. for 2 hours or more, after being let tocool down in a desiccator, the precipitate was weighed [mass: m₁ (g)].

Incidentally, the residual ratio of the residue after saccharificationis calculated by the following formula.

Residual ratio (%)=100×m ₁ /m ₀

The results are also shown in Table 1.

When the residue after saccharification was confirmed, the residue ofthe pulp fibers for saccharification No. 1 and No. 3 was configured bythe pulp fibers, and the residue of the pulp fibers for saccharificationNo. 2 was configured by the pulp fibers and the super absorbentpolymers.

In the above-mentioned Cellulase method, since the super absorbentpolymers are not decomposed in principle, it can be understood that thepulp fibers for saccharification No. 1 (residual ratio: 59 mass %) canbe more easily saccharified than the NBKP virgin pulp fibers (residualratio: 66 mass %).

TABLE 1 Example No. Example Comparative Comparative 1 example 1 example2 Pulp fibers for No. 1 No. 2 No. 3 saccharification No. InactivationSlaked lime Slaked lime — Ozone treatment Performed Not performed —Lignin content <0.10    0.15 0.16 ratio (mass %) Water contact angle (°)0  —^(a)) 13.9 Ash content ratio (mass %) 0.15 16 0.12 Beating degreereduction 360 — 275 speed (mL/h) Beating degree (mL)/time 138/120 —270/120 (minute) Residual ratio (mass %) of 59 76 66 residue aftersaccharification ^(a))There were much foreign matter, and could not bemeasured.

REFERENCE SIGNS LIST

-   31 treatment tank-   32 liquid mixture supply port-   33 treatment liquid discharge port-   43 ozone containing gas supply port-   51 liquid mixture-   52 treatment liquid-   53 ozone containing gas-   S36 ozone treatment process

1. A method of manufacturing pulp fibers for saccharification from pulpfibers of used hygiene products, comprising steps of: a preparation stepof preparing a treatment tank which includes a liquid mixture supplyport, and a treatment liquid discharge port and an ozone containing gassupply port that are arranged below the liquid mixture supply port, aliquid mixture supply step of supplying a liquid mixture which includessuper absorbent polymers and the pulp fibers that derive from the usedhygiene products and water, from the liquid mixture supply port to thetreatment tank, an ozone containing gas supply step of supplying ozonecontaining gas from the ozone containing gas supply port to a treatmentliquid in the treatment tank, a pulp fibers for saccharificationformation step of forming the pulp fibers for saccharification from thepulp fibers while dissolving at least a portion of the super absorbentpolymers in the treatment liquid, by, in the treatment tank, raising theozone containing gas while lowering the super absorbent polymers and thepulp fibers so as to make the ozone containing gas come into contactwith the super absorbent polymers and the pulp fibers, and a treatmentliquid discharge step of discharging the treatment liquid which includesthe pulp fibers for saccharification from the treatment liquid dischargeport, wherein the pulp fibers for saccharification have a lignin contentratio of 0.1 mass % or less.
 2. The method according to claim 1, whereinthe pulp fibers for saccharification have a water contact angle of 20°or less.
 3. The method according to claim 1, wherein the pulp fibers forsaccharification have a beating degree reduction speed of 300 mL/h ormore.
 4. The method according to claim 1 wherein in the pulp fibers forsaccharification formation step, the ozone containing gas is suppliedfrom the ozone containing gas supply port as microbubbles ornanobubbles.
 5. The method according to claim 1, wherein the treatmentliquid is acidic.
 6. The method according to claim 1, further comprisingan inactivation step of inactivating the super absorbent polymers by anacid, before the liquid mixture supply step.
 7. The method according toclaim 6, wherein the acid is an acid which can form a complex with metalions included in an excrement.
 8. The method according to claim 1,wherein the pulp fibers for saccharification have an ash content ratioof 0.65 mass % or less.
 9. The method according to claim 1, wherein inthe liquid mixture supply step, the liquid mixture is suppliedcontinuously from the liquid mixture supply port to the treatment tankin a first flow rate, and in the treatment liquid discharge step, thetreatment liquid is discharged continuously from the treatment liquiddischarge port in a second flow rate.
 10. The method according to claim1, further comprising a saccharification step of saccharifying the pulpfibers for saccharification, after the treatment liquid discharge step.11. An aqueous solution of pulp fibers for saccharification whichderives from used hygiene products that include pulp fibers and superabsorbent polymers, wherein the pulp fibers for saccharification have alignin content ratio of 0.1 mass % or less.
 12. The aqueous solution ofpulp fibers for saccharification according to claim 11, wherein the pulpfibers for saccharification have a beating degree reduction speed of 300mL/h or more.
 13. The aqueous solution of pulp fibers forsaccharification according to claim 11, wherein the aqueous solution ofpulp fibers for saccharification is acidic.
 14. The aqueous solution ofpulp fibers for saccharification according to claim 13, wherein theaqueous solution of pulp fibers for saccharification includes an acidwhich can form a complex with metal ions included in an excrement. 15.The aqueous solution of pulp fibers for saccharification according toclaim 1, wherein the pulp fibers for saccharification have an ashcontent ratio of 0.65 mass % or less.